Journal of the Korean Society for Precision Engineering

A Study on Numerical Thermal Design Techniques for High-power Propulsion Motors: Jaehun Choi, Chiwon Park, Heesung Park; J. Korean Soc. Precis. Eng. 2025;42(11):893-900.
Published online November 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.036

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Propulsion motors are vital components in marine propulsion systems and industrial machinery, where high torque and operational reliability are paramount. During operation, high-power propulsion motors generate considerable heat, which can adversely affect efficiency, durability, and stability. Therefore, an effective thermal management system is necessary to maintain optimal performance and ensure long-term reliability. Cooling technologies, such as water jackets, are commonly employed to regulate temperature distribution, prevent localized overheating, and preserve insulation integrity under high-power conditions. This paper examines the cooling performance of water jackets for high-power propulsion motors through numerical analysis. We evaluated the effects of three different cooling pipe locations and varying coolant flow rates on thermal balance and cooling efficiency. Additionally, we analyzed temperature variations in the windings and key heat-generating components to determine if a specific cooling flow rate and pipe configuration can effectively keep the winding insulation (Class H) within its 180^oC limit. The findings of this study highlight the significance of optimized cooling system design and contribute to the development of efficient thermal management technologies, ultimately enhancing motor reliability, operational stability, and energy efficiency.

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A Study on Temperature and Stress Distribution in a Lens under Multi-Stage Cooling Conditions in Progressive Glass Molding Processes: Ji Hyun Hong, Jeong Taek Hong, Dong Yean Jung, Young Bok Kim, Keun Park, Chang Yong Park; J. Korean Soc. Precis. Eng. 2025;42(2):157-168.
Published online February 1, 2025; DOI: https://doi.org/10.7736/JKSPE.024.122

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Glass Molding Process (GMP) is an effective method for producing precise optical elements such as lenses. This simulation study aimed to predict the distribution of temperature and stress within a lens during a multi-stage cooling process of GMP. To develop an accurate simulation model including molds and lens, thermal contact conductance and boundary conditions were determined by analyzing experimental and simulation results. The developed model was used to investigate changes in temperature and maximum principal stress within the lens, considering variations in cooling time, speed, and method at each cooling stage. Simulation results indicated that trends of maximum temperature difference and maximum principal stress within the lens were consistent over time. Results also showed that the maximum principal stress inside the lens increased significantly with additional cooling after uneven temperature distribution caused by a relatively short cooling time. Compared to simulation results of the cooling process involving contact only with bottom surface of the mold, contact cooling with both top and bottom surfaces showed decreased residual stress at the end of cooling and maximum temperature difference within the lens. However, the maximum principal stress could be higher during the cooling process involving both surfaces.

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Optimization of heating and molding temperatures in multi‐station glass molding for a meniscus aspheric lens
Jian Zhou, Baocheng Huang, Shihu Xiao, Lihua Li
International Journal of Applied Glass Science.2026;[Epub] CrossRef

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A Study on Numerical Analysis for Determination of Glass Molding Process Conditions for Glass Lenses: Jaehun Choi, Sajan Tamang, Heesung Park; J. Korean Soc. Precis. Eng. 2024;41(3):207-214.
Published online March 1, 2024; DOI: https://doi.org/10.7736/JKSPE.023.136

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The Glass Molding Process (GMP) produces large quantities of glass optical parts and provides the advantages of high molding accuracy, short production cycle, low cost, and little pollution. Developments in different sectors, such as cameras and telescopes, are prompting studies on the design of aspherical optical components. Modeling heat transfer and deformation at high temperatures are crucial aspects of studying glass because its properties are significantly influenced by temperature-induced phase changes. In this study, temperature changes and geometric deviations of lenses were studied with respect to heating, pressing, and cooling times and the heat capacity of the heater used. A 3D model was designed for the heating, pressing, and cooling steps, and heat transfer was subjected to numerical analysis considering the specific heat of glass and the temperature dependence of thermal conductivity. Lens molding temperature conditions were then analyzed with the heat capacity of the lens molding heating system. Lens molding conditions were derived by analyzing lens temperatures with respect to heating and cooling capacities at each process step.

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Precision glass aspherical lens manufacturing by compression molding: a review
Xiaohua Liu, Jian Zhou, Bo Tao, Yang Shu, Zexin Feng, Shih-Chi Chen, Yingying Zhang, Allen Y. Yi
Light: Advanced Manufacturing.2026; 7: 1. CrossRef
A Study on Temperature and Stress Distribution in a Lens under Multi-Stage Cooling Conditions in Progressive Glass Molding Processes
Ji Hyun Hong, Jeong Taek Hong, Dong Yean Jung, Young Bok Kim, Keun Park, Chang Yong Park
Journal of the Korean Society for Precision Engineering.2025; 42(2): 157. CrossRef

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Study of Condensation Heat Transfer Enhancement Using Micro/Nano Surface Modification Techniques: Younghun Shin, Kwon-Yeong Lee, Woonbong Hwang; J. Korean Soc. Precis. Eng. 2023;40(9):733-739.
Published online September 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.058

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Condensation is an important research topic that ensures increased energy efficiency. Our researchers aimed to optimize heat transfer in industrial heat exchanger tubes through surface modification. We first succeeded in fabricating superhydrophilic and superhydrophobic tubes using surface modification. We observed the condensation phenomenon on the outside of the tube and evaluated the heat transfer performance through a condensation experimental facility. As a result, we found that the condensation heat transfer efficiency of superhydrophobic tubes is superior to that of conventional tubes. However, the heat transfer efficiency of the superhydrophobic tube reduced with an increase in saturation. To improve performance degradation, superhydrophilic and superhydrophobic hybrid tubes were fabricated and evaluated for their potential to improve heat transfer efficiency. As a result, we found that the liquid film generated by filmwise condensation on the superhydrophilic surface swept past the residual droplets generated by dropwise condensation on the superhydrophobic surface, resulting in the best heat transfer performance. Our results break the stereotypes of previous studies and provide a new paradigm for achieving optimal heat transfer performance on large-area curved surfaces. This research is expected to be widely applied in a variety of industries where energy efficiency is critical.

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High-frequency Heat Treatment Simulation of Park Gear considering Coil Current Calculation and AISI 1552 Phase Transformation: Jin Kyu Choi, Seok Soon Lee; J. Korean Soc. Precis. Eng. 2023;40(5):399-407.
Published online May 1, 2023; DOI: https://doi.org/10.7736/JKSPE.022.136

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This study performed high-frequency heat treatment experiments and simulations of the park gear of an automobile transmission. The heating temperature and hardening depth were measured during high-frequency heat treatment. Moreover, by applying the resonance RCL circuit, the current value of the coil during high-frequency heat treatment, the electromagnetic and heat transfer material properties dependent on the temperature, and the phase transformation function were all applied to the simulation. In the high-frequency heat treatment experiment, the heating temperature was 977.4℃ and the 1st direction hardening depth was 1.5 mm, the 2nd direction hardening depth was 3 mm, and the 3rd direction hardening depth was 2.5 mm, and the reliability was verified by comparing the simulation heating temperature of 1,097℃ and the 1st direction predicted hardening depth of 1.6 mm, the 2nd direction predicted hardening depth of 2.8 mm, and the 3rd direction predicted hardening depth of 2.7 mm. The error rate of the heating temperature results was 12.2% whereas that of the hardening depth results was 7.1%.

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Analysis of Rapid Heating Performance in Multi-Layered Injection Mold System for CNT Surface Heating Element Application: Hyeon Min Lee, Young Bae Ko, Woo Chun Choi; J. Korean Soc. Precis. Eng. 2022;39(7):461-467.
Published online July 1, 2022; DOI: https://doi.org/10.7736/JKSPE.022.057

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As a heating method for RHCM (Rapid Heating Cycle Molding) various heating technologies such as high frequency induction heating, IR heating, gas heating, and high temperature steamare applied, but these methods are not satisfying high productivity due to low energy efficiency. Research has been actively conducted on RHCM based on planar heating elements with high heating efficiency, such as carbon nanotubes, which are applied. To apply the CNT web film to the RHCM, a heating element must be applied inside the injection mold and power must be applied. As electricity is directly applied to the CNT web film to generate heat, all mold parts in contact with the CNT web film must be insulated, and high heat transfer is required for rapid heating performance. Thus, in this study, a multi-layer structure mold module for insulation and high heat transfer was designed to enable rapid heating by applying a CNT web film as a heat source. To this end, we intend to present a research direction for the commercialization of rapid heating molds, by identifying the main variables of rapid heating through heating experiments by the mold metal and insulator materials, and reflecting them in the mold design.

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Analysis on the Warm Bending Process of Magnesium Alloy Sheet Using Additively Manufactured Polymer Die-Set: Hyung-Won Youn, Jun-Hyun Kyeong, Keun Park, Chang-Whan Lee; J. Korean Soc. Precis. Eng. 2021;38(10):775-783.
Published online October 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.042

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Research on the application of additively manufactured polymer (AMP) to the conventional manufacturing process is underway. In this study, an additively manufactured die-set (AMDS) was used and applied to the warm forming of the magnesium alloy. Heat transfer and coupled temperature-displacement analysis were conducted in the V-Bending and UBending processes to study the applicability of the AMDS to the warm-forming process of the magnesium alloy sheet (AZ31B). A heat transfer experiment was conducted to determine the thermal contact conductance between the AZ31B material and two types of die-set, the metal and AMP. V-Bending and U-Bending experiments were conducted at 373 and 423 K; reduction in temperature between metal die-set and the additively manufactured polymer die-set were compared. The springback after the bending process with different initial temperatures and die materials was investigated. The simulation model showed good agreement. The springback of AZ31B was more decreased with the additively manufactured polymer die-set than with the metal die-set. The stress of the additively manufactured polymer die-set in the bending process was very small. It was confirmed that in the AZ31B material, the additively manufactured polymer die set helps increase the formability and decrease springback by keeping the temperature of AZ31B better.

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Novel Design of Cooling Channel Utilizing Pin-Fin Vortex Generators in Electric Vehicle Driving Motor: Min-Gi Chu, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2021;38(7):491-500.
Published online July 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.023

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The objective of this study was to numerically accomplish the cooling performance of an electric vehicle driving motor depending on cooling channel design. Cooling performances of novel cooling channels were compared based on the temperature of coils and cooling channels as well as convection heat transfer coefficient in electric vehicle driving motors. Local axial positions of cooling channels at three different cases were marked for numerical comparison of heat transfer coefficients. Owing to forced convection by the boundary and flow conditions, the heat transfer coefficient of Case 3 at the location where pin-fins were attached in the cooling channel was improved 85.02 and 65.77% compared to Cases 1 and 2, respectively. In Case 3 with pin-fins having 50% of cooling channel length, the maximum temperature of the coil was 4.25% lower than that of Case 2 with pin-fins having 30% of the cooling channel length and 6.98% lower than that of Case 1 without pin-fins in the cooling channel. As a result, pin-fins finally diminished the maximum temperature of coils in Cases 2 and 3. Ultimately, Case 3 showed the best cooling performance for improving vehicle driving durability and developing next-generation electric vehicle cooling system technologies.

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A Study on Cooling Performance Augmentation of Water-Cooling and Optimization Design Utilizing Carbon Material in Electric Vehicle Secondary Battery: Seung Bong Hyun, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2020;37(7):519-528.
Published online July 1, 2020; DOI: https://doi.org/10.7736/JKSPE.020.043

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This research is to investigate the augmentation of cooling performance of water-cooling in the electric vehicle secondary battery. The research focused on the numerical study of heat transfer coefficients for cooling performance augmentation. To improve the water-cooling performance with three different inlet sections of water-cooling and five different mass flow rates, air-cooling, and water-cooling were compared. To compare the water-cooling performance, selected local positions for various temperature distributions were marked on the battery cell surface. The normalized local Nusselt number of the cooling area at the normalized height position indicated that the heat transfer coefficient of the combined section was averaging at 77.95 and 58.33% higher than that of the circle and square, respectively. The heat transfer coefficient with the normalized width by water-cooling at combined section was averaging at 5.15 times higher than that of the air-cooling. At the normalized height, the cooling performance at the water flow rates of 10 Lpm was averaging at 68-74% higher than that of 5 Lpm and 35-39% lower than that of 25 Lpm. Ultimately, the best cooling performance existed with the combined section, and the water flow rate of 10 Lpm was most appropriate, given the temperature difference and power consumption.

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Influence of heat-transfer surface morphology on boiling-heat-transfer performance
RenDa He, ZhiMing Wang, Fei Dong
Heat and Mass Transfer.2022; 58(8): 1303. CrossRef

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Development of Snow Melter with Horizontally Located Burner: Jang Yong Lee, Byung Yeol Bang, Hye Seong Kim, Gye Seok Lee, Soon Ha Ser, Sam Ho Im; J. Korean Soc. Precis. Eng. 2020;37(2):115-123.
Published online February 1, 2020; DOI: https://doi.org/10.7736/JKSPE.019.067

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Snow removal equipment in Korea has been developed to remove snow from roads by pushing it away with snow shovels or dispersing it into the air with snow blowers. However, in urban areas, it is difficult to use snow blowers. And piled snow on sidewalks not only hinder pedestrians from walking by, but also melt onto the roads during the day and freeze at night, causing traffic accidents. As a solution to this, there has been a need to develop a machine which melts snow on the place where high priority is given for snow clearing such as airports, roads of frequent black ice occurrence, and main traffic facilities. This paper describes the main design points and experimental results in developing the snow melting system composed of the burner, blower, water tank, etc. Hot air from the burner spouts into the water tank and some of it rises through the outer jacket where hot air is mixed with water in the tank, heating it. Hot air spouted to the bottom of water tank and hot water pouring from the head of the outer jacket are two sources of snow melting in designing the equipment.

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Study on Thermal Efficiency and Heat Transfer Analysis due to the Application of Snowmelting Deck of Carbon Fiber Heating Wire
Jeong-Keun Kim, Hong-Gun Kim, Hee-Jun Eun, Lee-Ku Kwac
Journal of the Korean Society of Manufacturing Process Engineers.2023; 22(2): 39. CrossRef

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Investigation of Influence of Laser Parameters and Powder Porosity on Thermal Characteristics in the Powder Bed of a SLM Process: Kwang-Kyu Lee, Ho-Jin Lee, Hyun-Sik Kim, Dong-Gyu Ahn, Yong Son; J. Korean Soc. Precis. Eng. 2019;36(8):761-769.
Published online August 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.8.761

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Heat transfer characteristics in the vicinity of irradiated region of the beam of a selective laser melting (SLM) process affect the creation of the melted region during the deposition. The creation of the molten pool is greatly influenced by laser parameters and powder characteristics. The goal of the paper is to investigate the influence of laser parameters and powder porosity on thermal characteristics in the vicinity of the molten pool of the SLM process through repeated finite element analyses (FEAs). The power and the scan speed are chosen as the laser parameters. The laser is assumed to be a volumetric Gaussian heat flux model. Materials of the powder and the substrate are chosen as SUS17-4PH and S45C, respectively. Temperature dependent thermal properties for those material are used to perform the FEA. An appropriate efficiency of the heat flux is predicted by comparing the results of FEAs and those of experiments. The influence of laser parameters on temperature distributions in the vicinity of the melted region and the formation of the molten pool is examined. In addition, the effects of porosity of powders on heat transfer characteristics in the vicinity of the melted region are discussed.

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Effects of Deposition Strategy and Preheating Temperature on Thermo-Mechanical Characteristics of Inconel 718 Super-Alloy Deposited on AISI 1045 Substrate Using a DED Process
Ho Kim, Kwang-Kyu Lee, Dong-Gyu Ahn, Hyub Lee
Materials.2021; 14(7): 1794. CrossRef

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A Study on the Convective Cooling Performance of the Secondary Battery in Electric Vehicle: Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2018;35(12):1157-1162.
Published online December 1, 2018; DOI: https://doi.org/10.7736/KSPE.2018.35.12.1157

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This study is to investigate convection cooling performance of the Secondary Battery of Electric Vehicle without heat sink. Research is focused on the comparative study on cooling between forced convection and natural convection cooling. Selected local locations for various temperature distributions had shown in the flow domain. Final temperature on the cell surface has been compared by forced convection with natural convection. According to the results of velocity and temperature distributions in the fluid domain, Buoyancy appear by density difference in the natural convection. Apparent vortex was detected in the fluid domain for forced convection. According to calculations of convective heat transfer coefficient between cell and atmosphere in the battery pack, average value of more 70-78% heat transfer coefficient increased by forced convection than natural convection. Average temperature value of the cell surface decreased up to 46.50% by forced convection. Due to vortex by air, cooling performance of forced convection is excellent. In addition, cooling on edge of the battery is better than heat source location.

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A Study on Heat Radiation Performance for Different Layout of Electric Vehicle Secondary Battery Cell
Seung Bong Hyun, Byeong Yeop Kim, Ji Hun Song, Dong-Ryul Lee
Journal of the Korean Society for Precision Engineering.2020; 37(4): 271. CrossRef

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Heat Transfer Analysis of Al Laminate Film on Battery Packaging Process: Jun Hwan Jang, Sang Ho Ahn; J. Korean Soc. Precis. Eng. 2018;35(11):1071-1077.
Published online November 1, 2018; DOI: https://doi.org/10.7736/KSPE.2018.35.11.1071

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In this paper, we simulated the heat transfer and heat sealing processes of a lithium polymer battery package using finite element method (FEM). We observed and calculated the temperature change of an aluminum (Al) laminate thin film and sealing block during different sealing times. We also calculated the temperature change of the sealing block during consecutive heat sealing processes. For the design of the sealing block for the manufacturing process, we set the heat sealing time and area of the sealing block of the lithium polymer battery packaging as variables in heat transfer analysis. We succeeded in predicting effective heat transfer behavior and calculating the heat loss in consecutive heat sealing processes in numerical values.

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Study on Thermal Efficiency and Heat Transfer Analysis due to the Application of Snowmelting Deck of Carbon Fiber Heating Wire
Jeong-Keun Kim, Hong-Gun Kim, Hee-Jun Eun, Lee-Ku Kwac
Journal of the Korean Society of Manufacturing Process Engineers.2023; 22(2): 39. CrossRef

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A Study on the Method for the Temperature Analysis of Side Wall for the Durability of Run-Flat Tires: Hyung Jin Kim, Jin Hwan Lee, Seong Rae Kim, Ki Deug Sung, Won Byoung Bae; J. Korean Soc. Precis. Eng. 2018;35(7):689-694.
Published online July 1, 2018; DOI: https://doi.org/10.7736/KSPE.2018.35.7.689

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Recently, the concern for safety is increasing as customers’ interest in Run-Flat tires, which can assure their safety in case of a puncture when driving, is growing. Run-Flat tires continues to evolve with the demands of customers who want the performance of general tires such as fuel-consumption and comfort from the basic Run-Flat function in the 1st generation. Run-flat tires are designed in various ways to cope with puncture in pneumatic tires. Currently, Run-flat tires in which Runflat Inserts are inserted into sidewalls of the tires are mainly used. In this study, we would like to propose a method to predict the temperature of sidewall of a Run-flat tires while running and how it affects the durability. We predicted the temperature distribution of sidewall during the running of Run-flat tires by calculating energy loss which is from the viscoelastic characteristic of rubber through deformation analysis of tires, and verified the prediction technique by comparing with the Run-flat endurance test.

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Study on the Pool Boiling Heat Transfer Characteristics of Aluminum Plate with Directional Surface Roughness: Jun Kim, Dong In Hong, Seok Min Kim; J. Korean Soc. Precis. Eng. 2018;35(5):485-491.
Published online May 1, 2018; DOI: https://doi.org/10.7736/KSPE.2018.35.5.485

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Rolled and extruded aluminum (Al) products have been widely used in heat exchanging systems using the boiling heat transfer (BHT) mechanism. The BHT coefficient can be increased on a rough surface due to the activation of the nucleation sites. In this study, the BHT characteristic of an Al plate with directional surface roughness (bare Al plate), which was generated in rolling or extrusion process, was measured and compared with the polished Al plates with non-directional surface roughness. The BHT coefficient of polished Al plate was increased with increasing surface roughness, saturated at ~300 nm (Sa). Although the surface roughness of the bare Al plate was 380-430 nm (Sa), the BHT coefficient of bare Al plates were lower than the polished Al plates with similar surface roughness. To examine the lower BHT coefficient of bare Al plate, the directional surface roughness was characterized by vertical and horizontal surface roughness values to the production direction, and we experimentally concluded the lower surface roughness value (horizontal surface roughness) was the dominant factor for the BHT characteristic of a rolled or extruded Al plate with directional surface roughness.

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Three-dimensional fin-tube expansion process to achieve high heat transfer efficiency in heat exchangers
Seong-Yeop Kang, Sae-Rom So, Yong Son, Seonghun Park, Man-Yeong Ha, Sang-Hu Park
Journal of Mechanical Science and Technology.2019; 33(9): 4401. CrossRef
Basic Experimental Study on Fin-Tube Expansion Process Using an Additive Manufactured Spiral-Grooved-Expanding Ball
Seong Yeop Kang, Changwan Han, Yong Son, Seong Hun Park, Sang Hu Park
Journal of the Korean Society for Precision Engineering.2019; 36(7): 667. CrossRef
Basic Experimental Study on Fin-Tube Expansion Process Using an Additive Manufactured Spiral-Grooved-Expanding Ball
Seong Yeop Kang, Changwan Han, Yong Son, Seong Hun Park, Sang Hu Park
Journal of the Korean Society for Precision Engineering.2019; 36(7): 667. CrossRef